JP3982157B2 - LED bar light source - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an LED bar light source used as an illumination light source for a document reading portion in a facsimile machine or an exposure light source for removing a latent image on a photosensitive drum in an electronic copying machine.
[0002]
[Prior art]
FIGS. 7 and 8 show examples of the configuration of the conventional LED bar light source of this type. First, the LED bar light source 80 shown in FIG. 7 is formed on one surface of a printed circuit board 81 having a strip shape, for example. A large number of LED lamps 82, such as chips, which are miniaturized, are arranged in close contact with each other and arranged in rows.
[0003]
Moreover, the LED bar light source 90 shown in FIG. 8 forms the reflection part 91a by forming an aluminum vapor deposition film etc. in the side surface of the light guide 91 formed in the rod shape with transparent resin. At this time, the light emitting portion 91b is formed in a slit shape along the axis of the light guide 91 in the reflecting portion 91a, and the LED lamp 92 is opposed to one end surface or both end surfaces of the light guide 91. Are to be arranged.
[0004]
[Problems to be solved by the invention]
However, in the above-described conventional configuration, first, the LED bar light source 80 shown in FIG. In addition to problems such as an increase in cost, the unevenness of brightness of the individual LED lamps 82 is directly reflected on the illumination surface, resulting in uneven illumination and insufficient performance. Has occurred. Further, since the LED lamps 82 are formed in a chip shape, wiring must be performed by wire bonds 82a or the like for each one, resulting in a problem that the number of production steps is enormous and the cost is increased.
[0005]
Further, in the LED bar light source 90 shown in FIG. 8, when the LED lamp 92 is installed only on one end face, it is substantially inversely proportional to the distance from the LED lamp 92 as shown by the characteristic curve K in FIG. As a result, the amount of light decreases and illumination unevenness occurs as in the case of the LED bar light source 80 described above.
[0006]
As a preventive measure, generally, an LED lamp 92 is installed at both ends of the light guide 91. In this case, however, the total length from the LED lamps 92 depends on the length of the light guide 91. The luminance distribution is likely to be a mountain shape with a high central portion or a valley shape with a low central portion. For example, the shape of the reflective portion 91a is set for each model of the LED bar light source 90, or the shape of the reflective portion 91a is adjusted. There is a problem that the production side becomes complicated.
[0007]
[Means for Solving the Problems]
In the present invention, as a specific means for solving the above-described conventional problems, an LED lamp is opposed to an end portion of a rod-shaped light guide, and light is emitted from a light emission portion provided on a side surface of the light guide. In the LED bar light source, the LED lamp is provided with one piece facing only one end portion of the light guide, and the light emitting portion has a distance from the LED lamp and the light guide body. The width in consideration of the distance from the mapping generated by the reflection of the LED lamp at the other end, and a substantially triangular wave shape in the longitudinal direction, the cross-sectional shape of the light guide is the light An LED bar light source characterized in that the back side of the emitting part is formed as a curved surface having a larger radius .
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Below, this invention is demonstrated in detail based on embodiment shown in a figure. 1 and FIG. 2 shows an LED bar light source according to the present invention. The LED bar light source 1 includes a lamp case 2, a case lid 3, a light guide 4, and an LED lamp 5. It is composed of
[0009]
The lamp case 2 is made of, for example, white resin, and a light guide groove 2a for fitting the light guide 4 is formed inside. The case lid 3 is also formed of a white resin or the like, similar to the lamp case 2, and a slit 3a for securing an optical path from the light guide 4 emitted from the light guide 4 is provided on the bottom surface. Yes.
[0010]
Further, the light guide 4 is formed of a transparent resin or the like in a substantially rod shape, and when assembled in the lamp case 2 and the case lid 3 as shown in FIG. The outer periphery of the lamp case 2 and the case lid 3 are substantially in close contact with each other except for the light emitting portion 4a to be described.
[0011]
In addition, in the present invention, the LED lamp 5 is opposed to only one end portion of the light guide 4 and light is incident on the inside of the conductor 4, and the other end portion is made of, for example, aluminum or silver. The mirror surface 4b is formed by vacuum evaporation or the like, and the light reaching the other end of the LED lamp 5 is folded back. The mirror surface 4b may be brought into close contact with the lamp case 2 to obtain the same action.
[0012]
3 to 5 show the light guide 4 in more detail, and FIG. 3 schematically shows the shape of the light emitting portion 4a. Here, the state when the light from the LED lamp 5 provided at one end propagates through the light guide 4 will be described. If the light guide 4 has an outer diameter and an inner surface at the other end face. If reflection is not performed, the luminance decreases in inverse proportion to the square of the distance from the end, that is, the LED lamp 5, to one side.
[0013]
Therefore, under the conditions as described above, if the area of the light emitting portion 4a is increased in proportion to the square of the distance from one end face, that is, the LED lamp 5, light is guided from the light emitting portion 4a. It becomes possible to make the brightness | luminance of the light radiated | emitted outside the body 4 constant.
[0014]
Here, in the actual light guide 4, internal reflection with the above-described outer diameter is performed, and folding reflection is performed at the other end portion. A reflected image of the lamp 5 is generated, and this reflected image acts as a light source in a pseudo manner, and the luminance change with respect to the distance from the LED lamp 5 of the light emitted from the light emitting portion 4a. Does not necessarily follow the law inversely proportional to the square of the distance described above, and exhibits a rather complicated aspect.
[0015]
Therefore, in actual implementation, it is practical to set the width D of the light emitting portion 4a by actual measurement. As an example, the cross-sectional shape of the light guide 4 is a substantially circular shape having a diameter of 3 mm and is long. Is about 272 mm, the width D (1) at one end is 0.4 mm, and the width D (2) at a position about 173 mm from one end is 1.4 mm. The width D changes substantially linearly.
[0016]
Further, the width D (3) at about 198 mm is 1.55 mm, and during this period, the rate of increase in the width D tends to be slightly blunted, which is a pseudo-occurrence occurring at the other end described above. It is thought that it is beginning to be affected by the light source. The width D (4) at the other end is 1.12 mm, and the required width D tends to decrease due to the influence of the pseudo light source.
[0017]
For the sake of easy understanding, the drawing shows the configuration of the light guide 4 of the present invention, in particular, the radial direction with respect to the length direction of the light guide 4 so that the shape of the light emitting portion 4a is clearly shown. Is shown in an extremely enlarged state. Further, the light guide 4 configured as described above can be formed easily and in large quantities with a uniform shape by being formed by resin molding using a mold, for example.
[0018]
FIG. 4 shows a cross-sectional shape orthogonal to the axis of the light guide 4. As a result of examination by the inventors for forming the present invention, the cross-sectional shape of the light guide 4 is about 3 mm in diameter, for example. When the round bar shape is used, the amount of light from the light emitting portion 4a increases when the back surface 4c side of the light emitting portion 4a is formed as a curved surface having a larger radius than when it is a perfect circle having a radius of 1.5 mm. There was found.
[0019]
Therefore, also in this embodiment, the back surface 4c side of the light emitting portion 4a is formed as a curved surface having a radius of 2 mm, and another portion having a radius of 1.5 mm, that is, a substantially half portion near the light emitting portion 4a is set to a radius of 1. The amount of light obtained from the light emitting portion 4a is increased by connecting with the connecting portion 4d of .75 mm.
[0020]
FIG. 5 shows a cross-sectional shape along the axis of the light guide 4. In the present invention, the light emitting section 4 a has a cross-sectional shape in the direction along the axis, for example, the apex angle α is approximately 110 °. Uniform shape with triangular wave. The apex angle α and the pitch P are determined to be optimum values according to the state in which the LED bar light source 1 is used, for example, the distance from the original to be read, and are limited to the above values. It is not something.
[0021]
Next, the operation and effect of the LED bar light source 1 of the present invention configured as described above will be described. FIG. 6 shows the output characteristic F of the light emitting portion 4a of the LED bar light source 1 when the above configuration is adopted, and a substantially uniform output is obtained over a range of about 40 to 270 mm.
[0022]
Here, when the output level is examined, the LED bar light source 1 of the present invention employs only one LED lamp 5 as a light emission source, but this kind of LED bar light source 1 is generally used. For example, it has been confirmed that it is necessary and sufficient for reading a manuscript with a facsimile machine or scanner, or for removing a latent image on a photosensitive drum in an electronic copying machine. Therefore, according to the present invention, the target illumination can be handled with one LED lamp 5, that is, with minimum power consumption.
[0023]
【The invention's effect】
As described above, according to the present invention, in the LED bar light source formed by causing the LED lamp to face the end portion of the rod-shaped light guide and emitting light from the light emitting portion provided on the side surface of the light guide, The LED lamp is provided with one piece facing only one end of the light guide, and the light emitting portion is a distance from the LED lamp and the LED at the other end of the light guide. The width is determined in consideration of the distance from the mapping generated by reflection of the lamp, and is substantially triangular in the longitudinal direction. The cross-sectional shape of the light guide is more on the back side of the light emitting portion. The LED bar light source is characterized by being formed as a curved surface with a large radius . First, the light from one LED lamp is set to a constant such as the distance from the light source, the width of the light emitting portion. Variable according to the level of brightness Therefore, it is possible to provide an LED bar light source with uniform characteristics without being affected by variations in individual LED lamps due to the use of a plurality of LED lamps, which is extremely effective in improving the quality of this type of LED bar light source. It has an excellent effect.
[0024]
Secondly, the purpose can be achieved with a single LED lamp, so that the power consumption of the LED bar light source can be minimized and power can be saved. In addition, it is possible to prevent performance degradation due to overheating or occurrence of failure, and to achieve extremely excellent effects in improving the performance and reliability of this type of LED bar light source.
[Brief description of the drawings]
FIG. 1 is a front view showing an LED bar light source according to the present invention.
FIG. 2 is a cross-sectional view taken along the line AA in FIG.
FIG. 3 is an explanatory view showing a light guide as a main part of the LED bar light source according to the present invention.
4 is a cross-sectional view taken along line BB in FIG.
5 is a cross-sectional view taken along the line CC of FIG.
FIG. 6 is a graph showing output characteristics of an LED bar light source according to the present invention.
FIG. 7 is an explanatory diagram showing a conventional example.
FIG. 8 is an explanatory diagram showing another conventional example.
FIG. 9 is a graph showing output characteristics of another conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... LED bar light source 2 ... Lamp case 3 ... Case lid 3a ... Slit 4 ... Light guide 4a ... Light emission part 4b ... Mirror surface 4c ... Back surface 4d ... Connection part 5 ... LED lamp

Claims (1)

In the LED bar light source formed by opposing the LED lamp to the end of the rod-shaped light guide and emitting light from the light emitting portion provided on the side surface of the light guide,
The LED lamp is provided with one piece facing only one end portion of the light guide, and the light emitting portion is a distance from the LED lamp and the LED at the other end of the light guide. It is a width that takes into account the distance from the map that is reflected by the lamp, and has a substantially triangular wave shape in the longitudinal direction,
The LED bar light source characterized in that the cross-sectional shape of the light guide is formed as a curved surface with a larger radius on the back side of the light emitting portion.

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